It has been proposed to place a constant diameter machined workpiece in Vee-blocks and to gage the diameter by a plurality of indicator probes, all calibrated to a single workpiece diameter, with the indicator probes contacting the bottom of the workpiece, and then the probes providing an electrical signal to be fed to a numerically controlled lathe to adjust cutting tool position. Since the probes are at the bottom center of the Vee-blocks, only a single diameter workpiece can be gaged and corrected in the lathe numerical control. This is shown in German Democractic Republic Pat. No. 151889.
It has also been suggested to use a rigid Vee-block in which a single diameter workpiece may be rested and the two legs of the Vee-block each carry a linear variable differential transformer to be spring-urged into contact with opposite sides of the outside diameter of the workpiece. This is used as an electrical gage of the diameter, but requires the complexity of two different transformers for measuring, plus a third receiving differential transformer to command the electrical signals.
Both of these references suggest structure which can be used with workpieces having only a constant diameter, but the great majority of workpieces have stepped diameters which need to be individually gaged. In the first reference, using a gage at the bottom center of the Vee-blocks is inherently only about one-ninth as accurate, for a given accuracy of instrumentation, compared with the present invention. In the second-mentioned system, only a single dimension part can be gaged, rather than parts of any dimension within a given range because the two linear variable displacement transformers are mounted directly on the Vee-block.